Az the OP is assuming the car was detected by camera, as her daughter had driven a lot through the city that day (as posted above somewhere) and would have passed a few cameras.

All road traffic cameras detect unregistered and uninsured vehicles on South Australian roads, in addition to police traffic enforcement.

The cameras (in SA) detect unregistered and uninsured vehicles even if the driver is not committing an offence - speeding, running a red light etc

If the daughter did get detected by camera,  a expiation notice will be sent out within 7 days.